Polyamide resin is widely used in various fields including electrical components, electronics components, and automobile components due to its excellent heat resistance, wear resistance, chemical resistance, and flame retardancy.
Due to the recent trend towards weight reduction in the automobile field, metal components are being replaced by plastic components. Polyamide resin compositions having excellent heat resistance have been used for engine rooms in automobiles which are under the hood areas that are exposed to high temperature environments for long periods of time.
In the automobile field, engines are being down-sized to increase fuel efficiency, leading to an increase of vehicles having turbo chargers.
In the case of an automobile using a turbo charger, the temperature inside the under hood increases more rapidly than conventional automobiles when high-powered. Thus, there is a growing need for materials having higher heat resistance for use in components that will be installed inside the under hood so that they can withstand the high temperature environment for long periods of time.
Furthermore, due to the problem that polyamide resin tends to have a low hydrolysis resistance, there are continued efforts to improve the hydrolysis resistance thereof.
Generally, to improve the hydrolysis resistance of polyamide resin, a method of adjusting the contents of amine and acid of an end of polyamide resin is used. This method, however, has limitations in improving properties at high temperatures for long periods of time to a satisfactory level.
A method of adding a carbodiimide additive to an aliphatic polyamide resin has been commonly used. Although this method may realize excellent effects in aliphatic polyamide resins that do not have high heat resistance, it cannot be easily applied to polyamide resins having high heat resistance due to the low heat resistance of the carbodiimide additive.
Therefore, there is a need for a polyamide resin composition having excellent hydrolysis resistance and also having resistance to gasoline, engine oil, and/or calcium chloride solution while maintaining high thermal stability even when exposed to high temperature environments for long periods of time.